"The road ahead will be long. Our climb will be steep. We may not get there in one year or even one term, but America -- I have never been more hopeful than I am tonight that we will get there. I promise you -- we as a people will get there," Obama said in Chicago, Illinois, before an estimated crowd of up to 240,000 people.

With Obama's projected win, he will become the first African-American to win the White House.

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"While the Democratic Party has won a great victory tonight, we do so with a measure of humility and determination to heal the divides that have held back our progress," Obama said. Watch more on the balance of power »

Flanked by American flags, Obama told the roaring crowd, "This is your victory."

"This was a long and hard fought campaign but the result was well worth the wait. Together, under the leadership of President Barack Obama, Vice President Joe Biden and a Democratic Congress, we will chart a better course to build a new economy and rebuild our leadership in the world."

"They understood his vision of a fairer and more just America and embraced it. They heard his call for a new generation of Americans to participate in government and were inspired. They believed that change is possible and voted to be part of America's future," the Massachusetts senator said in a statement.

As results came in Tuesday night, Obama picked up early wins in Pennsylvania and Ohio -- states considered must-wins for McCain.

Obama also won Virginia, a state that has not voted for a Democratic president since 1964.

Going into the election, national polls showed Obama with an 8-point lead.

Voters expressed excitement and pride in their country after casting their ballots in the historic election. Poll workers reported high turnout across many parts of the country, and some voters waited hours to cast their ballots. Read about election problems

Tuesday marks the end of the longest presidential campaign season in U.S. history -- 21 months.

Obama, 47, will now begin his transition to the White House. He will be sworn in at the 44th president on January 20, 2009.